1. Field of the Invention
The invention relates to the coating of flat glass and in particular to a method of coating flat glass by deposition of a coating from a coating gas and to an apparatus suitable for use in operating the method.
2. Description of the Prior Art
It is known to coat flat glass by chemical vapour deposition, and U.S. Pat. 4,469,045 describes a method and apparatus in which a coating gas is directed on to the surface of a hot ribbon of glass to be coated from a distributor extending across that surface transverse to the direction of movement of the ribbon, so that the gas flows substantially parallel to the glass under laminar flow conditions and uniformly across the width of the surface. A coating is deposited on the hot glass surface and the used coating gas is directed upwardly away from the glass surface along an exhaust channel formed between upstream and downstream guide walls. An extractor duct is provided in the region of the upper end of the exhaust channel, but is not connected to the exhaust channel.
When the method and apparatus described in U.S. Pat. No. 4,469,045 is used for the deposition of a reflecting silicon coating on a ribbon of hot glass, it is found that, after a period of operation, a silicon containing deposit builds up on the undersurface of the downstream toe, that is, the surface, adjacent the glass, of a guide member which limits the coating zone at its downstream end and diverts used gas away from the glass. This deposit eventually touches the glass and damages the coating formed on the glass, and the coating process has to be interrupted while the apparatus is removed from over the glass and cleaned to remove the deposit.